The process of wound healing has overlapping phases (coagulation phase, inflammatory phase and proliferative/remodelling phase) where constituents of the local microenvironment change over time and distinct cell types play different roles. Key cell players in the healing process are platelets, keratinocytes/epithelial cells, fibroblasts/myofibroblasts, different immune cells and endothelial cells. All tissues in the body can be injured and the healing process is somewhat specific to the organ, however the initial signals elicited by the damaged cells are similar. The most studied form of wound healing is in skin.
Tissue injury disrupts homeostasis, which initiates the coagulation process and activates the sympathetic nervous system. The platelets forming the blood clots release signals, mainly PDGF (platelet derived growth factor) and TGF (transforming growth factor) changing the local environment (Ref. 1). Injured and stressed cells release alarm signals that initiate the recruitment of immune cells such as neutrophils and monocytes. Within the wounded tissue, the immune cells secrete various chemokines, growth factors like VEGF-A, FGF, and EGF (vascular endothelial growth factor A, fibroblast growth factor, epidermal growth factor), ROS (reactive oxygen species) and matrix digestive enzymes, which change the microenvironment and allow the healing process to enter the proliferative phase where failing and dead tissue is removed by macrophages. Cells from the wound edges, such as fibroblasts and keratinocytes, migrate inwards to the wound centre and cover the wound surface with a layer of collagen and extracellular matrix. The fibroblasts within the wound are then transformed into myofibroblasts expressing contractile α-SMA (α-smooth muscle actin) allowing the wound to contract and finally close. The transition from fibroblasts into myofibroblasts is dependent on signals from the microenvironment, some of which originate from immune cells, mainly macrophages. During this process, blood vessels are growing into the newly formed tissue, the granulation tissue. Blood flow to the adjacent area is normally increased during this phase to increase the availability of oxygen and nutrients, in addition to immune cell recruitment and migration to the afflicted site.
Following wound closure, the afflicted site becomes re-epithelialized by keratinocytes/epithelial cells whereby the integrity of the organ barrier is regained. Even after wound closure, some tissue remodelling occurs to normalize the matrix structure and the majority of involved immune cells either die or leave the site. Also at this stage dead or dying cells are ingested and cleared (phagocytosed) by the remaining tissue macrophages (Ref. 1). Faster wound healing reduces complications and discomfort to the patient,
Impaired or delayed cutaneous or mucosal wound healing is a worldwide clinical problem causing pain, direct exposure to pathogens, loss of tissue function and loss of temperature and fluid balance regulation. There are several conditions where the tightly regulated wound healing process is impaired and the cutaneous or mucosal wounds remain unhealed for longer time periods than normal, which in worst case become chronic.
Reduced blood flow to the skin, especially in extremities, significantly reduces the efficiency of the healing process. There are several clinical conditions where the skin perfusion is either reduced or the function of the vasculature is impaired such as PAD (peripheral artery disease), intermittent claudication, vein insufficiency or vessel obstruction by arteriosclerotic plaques. Impaired blood flow to the wound area results in shortage of oxygen and nutrients and the cells aiding in the tissue remodeling either die from necrosis or are unable to perform their tasks on site. Also the surrounding tissue will if not sufficiently supplied lose functionality and ultimately start to die. Tissues are during the remodeling phase very metabolically active and have high oxygen consumption.
Another factor impairing cutaneous wound healing is hyperglycemia and diabetes mellitus. During hyperglycemic conditions cell signaling and immune system functions are impaired. Complications resulting from diabetes include microvascular changes and damage to peripheral neurons. As a result, diabetic patients often develop chronic wounds on their feet, commonly called diabetic foot. The available treatment for these patients today is removal of dead tissue using surgical debridement or collagenase together with systemic antibiotic treatment and closed wound dressing. There are experimental studies where growth factors and biomaterials have been applied to chronic wounds (Ref. 2).
The stromal cell-derived factor 1 (SDF-1) also known as C-X-C motif chemokine 12 (CXCL12) is a chemokine protein that in humans is encoded by the CXCL12 gene. WO 2009/079451 discloses a method for promoting wound healing in a subject, comprising administering directly to the wound or an area proximate the wound an amount of SDF-1 effective to promote healing of the wound of the subject.
Certain probiotics (Lactobacillus reuteri ATCC PTA 6475) have been shown to facilitate wound healing if supplemented in the drinking water during the healing process (Ref. 9), i.e. the bacteria were ingested. Further, supernatants from culture of Lactobacillus plantarum have been demonstrated to inhibit biofilm production by Pseudomonas aeruginosa, commonly infecting chronic wounds (Ref. 10).
It has surprisingly been found that lactic acid bacteria which are modified, according to the present invention, to express specific proteins, such as cytokines, are useful for promoting wound healing. Lactic acid bacteria are sparsely present on the human skin (Ref. 13) and are not the expected choice of bacteria to use for any intervention on the skin. Lactobacilli are difficult to work with since they grow relatively slowly and require special medium and conditions in comparison with more commonly used bacteria like E. coli and S. aureus. Further, Lactobacilli have limited intracellular machinery for transcription, translation and protein folding. For this reason, nucleotide sequences coding for heterologous proteins have to be optimized to fit the specific bacterial strain.
The different phases of wound healing comprise distinct key events that could be altered to change the healing process. Vascular remodeling during the healing process is highly dependent on induction of hypoxia inducible factor 1α (HIF-1α) that regulates the expression of VEGF-A (vascular endothelial growth factor A) and a range of chemokines, such as CXCL12 (also known as SDF-1; SEQ ID NO: 3 and 6). CXCL12 is constitutively expressed in tissues and acts through the receptor CXCR4 found on leukocytes and endothelial cells inducing multiple cellular actions (Ref. 3). CXCL12 is found in high levels in macrophages specialized in tissue remodeling (Ref. 4). Dermal overexpression of CXCL12 using lentiviral vectors improves wound healing in diabetic mice (Ref. 5).
Another recently discovered chemokine is CXCL17 (SEQ ID NO: 9 and 12), which has similar effects on the phenotype of tissue macrophages as CXCL12. In similarity with CXCL12, CXCL17 is co-regulated with VEGF-A measured in cell culture (Ref. 6). CXCL17 is found mainly in mucosal tissues and have been reported to be directly antimicrobial to pathogenic bacteria that are also found on skin whilst showing no effect on survival of Lactobacillus casei (Ref. 7).
A further protein of interest is Ym1 (SEQ ID NO: 15 and 18), which is a chitinase-like protein. Chitin is a common polysaccharide in bacterial biofilm. Ym1 both counteracts biofilm production and induces macrophage functions important for tissue remodeling and wound healing and is specific to macrophages since it is not taken up by either vascular cells or epithelial cells (Ref. 8).
Consequently, in a first aspect the invention provides a recombinant plasmid which is capable of expressing a protein in lactic acid bacteria (i.e. when transformed into a lactic acid bacterial cell), wherein the said protein is useful for improving wound healing, such as cutaneous or mucosal wound healing, in a human or animal subject. Preferably, the said protein is useful for wound healing due to its capability of targeting immune cells such as macrophages and their precursors. Preferably, the said protein is a cytokine or chemokine. Most preferably, the said protein is chosen from the group consisting of murine CXCL12, in particular murine CXCL12-1α (SEQ ID NO: 3); human CXCL12, in particular human CXCL12-1α (SEQ ID NO: 6); murine CXCL17 (SEQ ID NO: 9); human CXCL17 (SEQ ID NO: 12); murine Ym1 (SEQ ID NO: 15); and human Ym1 (SEQ ID NO: 18).
This first aspect of the invention more particularly provides a plasmid which is capable of expressing a recombinant protein in lactic acid bacteria (i.e. when transformed into a lactic acid bacterial cell), wherein said plasmid comprises a nucleotide sequence encoding a protein selected from CXCL12, CXCL17 and Ym1.
More specifically the nucleotide sequence may encode murine CXCL12, in particular murine CXCL12-1α; human CXCL12, in particular human CXCL12-1α; murine CXCL17; human CXCL17; murine Ym1; or human Ym1.
In one embodiment, the plasmid comprises a nucleotide sequence encoding a protein selected from murine CXCL12-1α having an amino acid sequence as shown in SEQ ID NO: 3 or 2, or an amino acid sequence with at least 80% sequence identity thereto; human CXCL12-1α having an amino acid sequence as shown in SEQ ID NO: 6 or 5, or an amino acid sequence with at least 80% sequence identity thereto; murine CXCL17 having an amino acid sequence as shown in SEQ ID NO: 9 or 8, or an amino acid sequence with at least 80% sequence identity thereto; human CXCL17 having an amino acid sequence as shown in SEQ ID NO: 12 or 11, or an amino acid sequence with at least 80% sequence identity thereto; murine Ym1 having an amino acid sequence as shown in SEQ ID NO: 15 or 14, or an amino acid sequence with at least 80% sequence identity thereto; and human Ym1 as shown in SEQ ID NO: 18 or 17 or an amino acid sequence with at least 80% sequence identity thereto.
More particularly, the plasmid is for use in expressing a protein in lactic acid bacteria and is accordingly provided, or adapted, for such use (e.g. it is designed, selected, adapted or modified for specific or particular use in lactic acid bacteria). Thus in one embodiment the plasmid is for specific expression in lactic acid bacteria, as compared to bacteria or microorganisms generally. The plasmid may be adapted for expression in lactic acid bacteria by means of its regulatory elements (regulatory sequences) and/or coding sequences, e.g. which are selected or modified for expression in lactic acid bacteria.
Accordingly, in a more particular aspect the plasmid comprises one or more regulatory (i.e. expression control) sequences which permit expression, or which are specific for expression, in lactic acid bacteria. Thus, the plasmid may contain expression control sequences derived from, or suitable for, or specific for, expression in lactic acid bacteria. Appropriate expression control sequences include for example translational (e.g. start and stop codons, ribosomal binding sites) and transcriptional control elements (e.g. promoter-operator regions, termination stop sequences), linked in matching reading frame with the nucleotide sequence(s) which encode the protein(s) to be expressed. The regulatory sequences(s) are operably linked to a nucleotide sequence encoding said protein, such that they drive, or control, expression of the protein. The plasmid may be introduced into a lactic acid bacterial cell. Suitable transformation techniques are well described in the literature. The bacterial cell may be cultured or otherwise maintained under conditions permitting expression of said protein from the plasmid. This may include conditions in a wound in a subject.
In one embodiment the promoter in the plasmid which controls expression of the protein is a promoter which permits, or which is specific for, expression in lactic acid bacteria. Thus the plasmid may comprise a nucleotide sequence(s) encoding the protein(s), under the control of (or operably linked to) a promoter capable of expressing the protein in lactic acid bacteria. In a particular preferred embodiment the plasmid comprises a lactic acid bacteria promoter, that is the promoter which controls expression of the protein(s) is a promoter which is derived from a lactic acid bacterium, or more particularly which is obtained or derived from a gene expressed in a lactic acid bacterium.
In some embodiments, in addition to a lactic acid bacterial promoter, the plasmid may also contain other regulatory elements or sequences obtained or derived from lactic acid bacteria to control expression of the protein(s). Thus for example such other lactic acid bacterial expression control elements or sequences may include enhancers, terminators and/or translational control elements or sequences as discussed above. In some embodiments the plasmid may also contain regulatory elements or sequences which control or regulate expression from the promoter e.g. operator sequences etc. or one or more regulatory genes, as discussed further below.
Alternatively or additionally the plasmid may be adapted (or modified etc.) for use in lactic acid bacteria by virtue of the nucleotide sequences encoding the protein(s) being codon-optimised for expression in lactic acid bacteria.
In a preferred embodiment the promoter for expression of the protein is a regulated (regulatable) or inducible promoter. Thus, expression of the protein may be controlled or regulated (e.g. initiated, for example at a desired or appropriate time) by providing or contacting the bacteria with a regulatory molecule or inducer which activates or turns on (induces) the promoter. This is advantageous in the context of delivery of the protein to a wound.
Accordingly, a further aspect of the invention provides an expression system for use in expressing a protein in lactic acid bacteria, said expression system comprising (i) a plasmid as defined herein, wherein said plasmid comprises a nucleotide sequence encoding a said protein under the control of an inducible promoter capable of expressing the protein in lactic acid bacteria; and (ii) an inducer (or regulatory molecule) for the promoter. The expression system may conveniently be provided in the form of a kit comprising components (i) and (ii) above.
A still further aspect of the present invention is a bacterium, or bacteria, (i.e. a bacterial cell or strain) transformed with (i.e. comprising) a plasmid of the invention, as defined herein. Particularly, the bacterium is a lactic acid bacterium and the invention accordingly provides lactic acid bacteria (or a lactic acid bacterium) comprising a plasmid of the invention, as defined herein. Alternatively expressed, this aspect of the invention provides a bacterium (or bacterial cell) into which a plasmid of the invention has been introduced.
As described further herein, the plasmids and bacteria of the invention are useful for promoting healing, and thus have particular utility in promoting healing of wounds, which are defined herein to include injured tissue generally (see further below). Accordingly further aspects of the invention provide such plasmids and bacteria for use in therapy, and more particularly for use in wound healing.
The bacteria may be provided for administration to a wound in a subject to be treated in the form of a pharmaceutical composition. Accordingly a still further aspect of the invention provides a pharmaceutical composition comprising bacteria of the invention as defined herein, together with at least one pharmaceutically acceptable carrier or excipient.
More generally, the invention provides a probiotic product comprising the bacteria of the invention.
Such a product, or pharmaceutical composition, may conveniently take the form of a wound dressing comprising the bacteria of the invention. Thus, in a further aspect the invention provides a wound dressing comprising bacteria of the invention as hereinbefore defined, together with at least one dressing material.
A yet further aspect of the invention provides use of a plasmid or of bacteria of the invention as defined herein for the manufacture of a medicament (or a probiotic product) for use in wound healing.
Also provided is a method of treating a subject to heal a wound, said method comprising administering to said subject, or to the wound in said subject, an amount of bacteria of the invention as defined herein effective to promote healing of the wound.
Another aspect of the invention provides a kit for healing wounds, said kit comprising:                (i) lactic acid bacteria comprising a plasmid of the invention as defined herein, wherein said plasmid comprises a nucleotide sequence encoding a said protein under the control of an inducible promoter capable of expressing the protein in lactic acid bacteria; and        (ii) an inducer (or regulatory molecule) for the promoter.        
A still further aspect of the invention comprises a pharmaceutical product (e.g. a kit or combination product) comprising;                (i) lactic acid bacteria comprising a plasmid of the invention as defined herein, wherein said plasmid comprises a nucleotide sequence encoding a said protein under the control of an inducible promoter capable of expressing the protein in lactic acid bacteria; and        (ii) an inducer (or regulatory molecule) for the promoter,        
as a combined preparation for separate, sequential or simultaneous use in wound healing (or for treating a wound in a subject).
The term “wound healing” is used broadly herein to include any aspect of promoting or improving the healing of a wound. Thus, the various aspects of the invention set out above may alternatively be defined with respect to a utility of the plasmids or bacteria in promoting or enhancing or improving wound healing or simply promoting or enhancing healing.
Wound healing may accordingly include or encompass any effect which results in faster wound healing, or more complete healing of a wound or indeed any amelioration or improvement in the healing of a wound, e.g. reduced healing time, for example reduced time to achieve partial or complete closure of a wound, improved wound appearance (e.g. the appearance of a healed or healing wound), reduced or improved scar formation, the promotion of healing of a chronic or recalcitrant wound etc. (i.e. the application of the bacteria of the invention to a wound may induce, or cause, or start, the healing of a wound which has up to now not healed or shown any signs of healing). Wounds are discussed in more detail below.
The subject having a wound to be treated may be any human or animal subject, including for example domestic animals, livestock animals, laboratory animals, sports animals or zoo animals. The animal is preferably a mammalian animal, but other animals, e.g. birds are included. Thus the animal may be a primate, a rodent (e.g. a mouse or rat), or a horse, dog or cat. Most preferably the subject is a human.
Lactic acid bacteria (LAB) or Lactobacillales are a clade of Gram-positive, low-GC, acid-tolerant, generally nonsporulating, nonrespiring, either rod-shaped (bacillus), or spherical (coccus) bacteria which share common metabolic and physiological characteristics. These bacteria produce lactic acid as the major metabolic end product of carbohydrate fermentation and are characterized by an increased tolerance to acidity (low pH range). These characteristics of LAB allow them to outcompete other bacteria in a natural fermentation because LAB can withstand the increased acidity from organic acid production (e.g. lactic acid). Thus LAB play an important role in food fermentations, as acidification inhibits the growth of spoilage agents. Several LAB strains also produce proteinaceous bacteriocins which further inhibit spoilage and growth of pathogenic microorganisms. LAB have generally recognized as safe (GRAS) status and are amongst the most important groups of microorganisms used in the food industry.
The core genera that comprise the lactic acid bacteria clade are Lactobacillus, Leuconostoc, Pediococcus, Lactococcus, and Streptococcus, as well as the more peripheral Aerococcus, Carnobacterium, Enterococcus, Oenococcus, Sporolactobacillus, Tetragenococcus, Vagococcus, and Weissella. Any lactic acid bacteria from these genera are included within the scope of the present invention, but particularly bacteria from the genera Lactobacillus or Lactococcus. 
The plasmid may encode one or more of said proteins. Thus it may encode a combination of a CXCL12, CXCL17 and/or a Ym1 protein (e.g. 2 or more of CXCL12, CXCL17 or Ym1). Alternatively, it may encode 2 or more types of a CXCL12, CXCL17 and/or Ym1 protein (e.g. both murine and human CXCL12 etc.). Where more than one protein is encoded, the protein may be expressed from a nucleotide sequence encoding the proteins under the control of a single promoter, or more than one promoter may be used. For example, each protein may be expressed from a separate promoter, which may be the same or different. Techniques for expression of 2 or more proteins together from the same plasmid are well known in the art and include for example translational coupling techniques etc., means for achieving this are known and available in the art. For example multiple transgenes can be expressed simultaneously under one promoter using P2A and T2A sequences.
The CXCL12, CXCL17 or Ym1 protein may be a native or natural protein (i.e. the nucleotide sequence may encode a protein having an amino acid sequence as found in nature) and may be from any species in which these proteins occur. Generally the protein will be a mammalian protein and as indicated above human and murine proteins are preferred. However, the native nucleotide sequences or protein sequences may be modified, for example by one or more amino acid additions, insertions, deletions and/or substitutions, as long as the function or activity of the protein is not substantially or significantly altered, e.g. as long as the activity of the protein is substantially retained. The protein may be a fragment or truncated variant of a natural protein. For example, a sequence-modified variant protein may exhibit at least 80, 85, 90 or 95% of the activity of the parent protein from which it is derived. This may be assessed according to tests known in the art for activity of the protein in question. For example, activity can be measured in systems of receptor phosphorylation or calcium flux upon ligation in culture cells treated with the protein, in systems of cell chemotaxis in vitro or in vivo in models of cell recruitment to the infected protein. An in vitro assay based on chemotaxis is described in Refs. 22 and 32. Ref. 33 describes a further in vitro chemokine activity test which might be used. The terms “CXCL12”, “CXCL17” or “Ym1” thus include not only the native proteins but also functionally equivalent variants or derivatives thereof. The proteins may thus be synthetic or sequence-modified variants, or may comprise one or more other modifications, e.g. post-translational modifications etc.
As mentioned above, the encoded proteins may have the amino acid sequences indicated above for the native human or murine proteins, namely SEQ ID NOS. 3 and 6 for murine and human CXCL12 respectively, 9 and 12 for murine and human CXCL17 respectively, and 15 and 18 for murine and human Ym1 respectively, or an amino acid sequence having at least 80% sequence identity to any aforesaid sequence. Advantageously, as further indicated above, the nucleotide sequences encoding these native proteins may be codon-optimised for expression in lactic acid bacteria. This may result in a modified amino acid sequence of the protein encoded. For example codon optimised sequences may encode sequences such as secretion sequences suitable, (or better suited) for lactic acid bacteria. Thus the “optimized” protein encoded by a codon-optimised nucleotide sequence may include an altered or substituted leader or signal sequence (e.g. secretory sequence) as compared to the native protein. In a preferred embodiment the mature or cleaved form of the protein encoded by the codon optimised sequence is identical to the native protein. Proteins encoded by codon-optimised nucleotide sequences may have an amino acid sequence as shown in SEQ ID NOS. 2, 5, 8, 11, 14, or 17 as listed in Table IV below. Thus, the protein encoded by the plasmid may have an amino acid sequence as shown in SEQ ID NOS. 2 and 5 for murine and human CXCL12 respectively, 8 and 11 for murine and human CXCL17 respectively, and 14 and 17 for murine and human Ym1 respectively, or an amino acid sequence having at least 80% sequence identity to any aforesaid sequence.
In other embodiments the encoded protein(s) may have an amino acid sequence which has at least 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89% 90%, 91% 92% 93%, 94%, 95%, 96%, 97%, 98% or 99% sequence identity with any aforesaid amino acid sequence.
Sequence identity may readily be determined by methods and software known and readily available in the art. Thus, sequence identity may be assessed by any convenient method. However, for determining the degree of sequence identity between sequences, computer programs that make multiple alignments of sequences are useful, for instance Clustal W (Ref. 24). Programs that compare and align pairs of sequences, like ALIGN (Ref. 25), FASTA (Ref. 26 and Ref. 27), BLAST and gapped BLAST (Ref. 28) are also useful for this purpose, and may be used using default settings. Furthermore, the Dali server at the European Bioinformatics institute offers structure-based alignments of protein sequences (Ref. 29, Ref. 30 and Ref. 31). Multiple sequence alignments and percent identity calculations may be determined using the standard BLAST parameters, (e.g. using sequences from all organisms available, matrix Blosum 62, gap costs: existence 11, extension 1). Alternatively, the following program and parameters may be used: Program: Align Plus 4, version 4.10 (Sci Ed Central Clone Manager Professional Suite). DNA comparison: Global comparison, Standard Linear Scoring matrix, Mismatch penalty=2, Open gap penalty=4, Extend gap penalty=1. Amino acid comparison: Global comparison, BLOSUM 62 Scoring matrix.
Variants of the naturally occurring polypeptide sequences as defined herein can be generated synthetically e.g. by using standard molecular biology techniques that are known in the art, for example standard mutagenesis techniques such as site-directed or random mutagenesis (e.g. using gene shuffling or error prone PCR).
Derivatives of the proteins as defined herein may also be encoded. By derivative is meant a protein as described above or a variant thereof in which the amino acid is chemically modified e.g. by glycosylation and such like etc.
Where a protein comprises an amino acid substitution relative to the sequence of the native protein, the substitution may preferably be a conservative substitution. The term “a conservative amino acid substitution” refers to any amino acid substitution in which an amino acid is replaced (substituted) with an amino acid having similar physicochemical properties, i.e. an amino acid of the same class/group. For instance, small residues Glycine (G), Alanine (A) Serine (S) or Threonine (T); hydrophobic or aliphatic residues Leucine (L), Isoleucine (I); Valine (V) or Methionine (M); hydrophilic residues Asparagine (N) and Glutamine (Q); acidic residues Aspartic acid (D) and Glutamic acid (E); positively-charged (basic) residues Arginine (R), Lysine (K) or Histidine (H); or aromatic residues Phenylalanine (F), Tyrosine (Y) and Tryptophan (W), may be substituted interchangeably without substantially altering the function or activity of the protein.
As indicated above, it is preferred to use an inducible promoter for expression of the protein. By “inducible” is meant any promoter whose function (i.e. activity, or effect in allowing or causing transcription of the coding nucleotide sequence) can be regulated or controlled. The term “inducible” is thus synonymous, and may be used interchangeably with “regulatable” (or “regulated”). Thus, there is not constitutive expression of the protein. Accordingly, expression of the protein may be induced, or turned on (or more particularly turned on and off). More particularly, expression may be induced, or turned on for a finite or defined time. This may be because expression ceases after a period of time, and/or because the bacterial cells die.
In some embodiments there may be no expression (transcription) from the promoter until the promoter is induced (or alternatively termed, activated). However, as with any biological system, lack of activity may not be absolute and there may be some basal promoter activity in the absence of promoter activation or induction. However, in a preferred embodiment any basal expression of the uninduced promoter is low, minimal, or insignificant, or more preferably de minimis or negligible. Thus, expression from the inducible promoter is advantageously measurably or demonstrably increased when the promoter is induced compared to the promoter when it is not induced.
Inducible promoters are well known in the art, including inducible promoters for use in lactic acid bacteria and any appropriate inducible promoter may be used, suitable for expression in lactic acid bacteria.
An inducible promoter may be induced (or activated) in the presence of an inducer or activator molecule, which may act directly or indirectly on the promoter, and which may be added to induce the promoter, or more generally to cause or enable induction or activation of the promoter, and permit expression of the protein, or it may be induced (or activated) by a change in conditions of the bacteria containing the plasmid, e.g. by introducing a change of conditions to the lactic acid bacteria, e.g. starvation or depletion of a particular nutrient. An inducer of the promoter may be encoded by a regulatory gene, which in an embodiment may itself be induced or activated. The term “inducer” is thus used broadly herein to include any regulatory molecule, or indeed any permissive condition, which may activate or turn on an inducible promoter, or allow or cause an inducible promoter to be induced. Thus, induction of an inducible promoter may comprise the introduction of (e.g. contacting the lactic acid bacteria containing the plasmid with) a regulatory molecule or of a condition permissive to promoter induction (activation). In some embodiments the inducer can be an activation peptide. This may act directly, or indirectly to induce the promoter, for example as described further below.
As noted above, promoters obtained or derived from lactic acid bacteria are preferred. These may be native promoters or modified or mutant promoters. A suitable promoter may for example be identified by growing lactic acid bacteria in a wound, and by determining which genes are expressed, or upregulated in the bacteria in the wound. The promoters from such genes may then be identified. Alternatively a number of different promoters and expression systems in or for use in lactic acid bacteria have been identified and described or available in the art, including expression plasmids containing such promoters or expression systems for use in LAB. Any such known plasmid or expression system may be used as the basis for the recombinant plasmid of the invention.
Various inducible expression systems are known in the art for use with LAB such as Lactobacilli. One example includes an auto-inducing system based on the manganese starvation-inducible promoter from the manganese transporter of L. plantarum NC8 as described in Ref. 19. This system does not require the addition of external inducers for recombinant protein production.
Duong et al. (Ref. 20) describe expression vectors for use with lactobacilli based on the broad range pWV01 replicon and containing promoters from operons involved in fructooligosaccharide (FOS), lactose or trehalose metabolism or transport, or in glycolysis. Such promoters may be induced by their specific carbohydrate and repressed by glucose.
More particularly, the inducible expression system may comprise inducible promoters involved in the production of LAB proteins, and in particular bacteriocins. The activity of such promoters may be controlled by a cognate regulatory system based on the bacteriocin regulon, for example a two-component regulatory (signal transduction) system which responds to an externally added activator peptide (i.e. an inducer/regulatory molecule in peptide form) and genes encoding a histidine protein kinase and response regulator necessary to activate this promoter upon induction by an activator peptide.
In an embodiment the expression system may be based on the nisin-controlled expression (NICE) system, based on the combination of the nisA promoter and the nisRK regulatory genes. This system is based on the promoters and regulatory genes from the Lactococcus lactis nisin gene cluster and has been used to develop regulated gene expression systems for lactococci, lactobacilli and other Gram-positive bacteria (reviewed briefly in Ref. 15 and Ref. 21). Whilst the NICE systems are efficient and well regulated in Lactococci, these systems can exhibit significant basal activity. This can be circumvented by integrating the histidine kinase and response regulator genes in the chromosome, limiting the expression systems to specially designed host strains.
In another embodiment the expression system may be based on the genes and promoter involved in the production of class II bacteriocins sakacin A (sap genes) by the sakacin A regulon or sakacin P (spp genes) by the sakacin P regulon. Such vectors are known as pSIP vectors and contain a promoter element derived from either the sakacin A or the sakacin P structural gene with an engineered NcoI site for translational fusion cloning. A variety of such vectors containing different promoters from the regulons and/or different replicons are described in Ref. 21 and Ref. 15 and any of these vectors could be used as the basis for the recombinant plasmid of the invention.
In a representative embodiment the promoter may be the PsapA, PsppA or PorfX promoter from the sakacin A or P regulon, together with its associated or cognate regulatory genes.
In a particularly preferred embodiment the plasmid contains the pSH71 replicon, the PorfX promoter from the sakacin P regulon and the cognate regulatory genes, based on the vector pSIP411 depicted in FIG. 12 and described in Ref. 21. Plasmid pSIP411 is designated pLAB112 in the present application. The inducer for use in such an embodiment is preferably an activation peptide based on the peptide SppIP, e.g. an activation peptide having the sequence of SEQ ID NO: 19, or an amino acid sequence with at least 80% (or more particularly at least 85, 90 or 95) sequence identity thereto. In a preferred embodiment the said recombinant plasmid is derived from the plasmid designated pLAB112 having the nucleotide sequence shown in SEQ ID NO: 20.
The use of an inducible promoter (or inducible expression system) may provide the advantage of a more controlled, and in particular prolonged expression of the protein in the wound setting i.e. when the bacteria are administered to the subject or to the wound. For a better effect in promoting wound healing it is advantageous for the protein to be expressed by the bacteria for a period of time at the site of the wound (e.g. at the wound surface), e.g. for at least 40, 45, 50, 55 or 60 minutes, notably for at least one hour, or more. Thus the protein may be expressed for a finite, a defined or a prolonged period of time. Results presented in the Examples below show that using plasmids and bacteria according to the present invention, the protein may be expressed for a period of about an hour at the wound surface. The plasmids and bacteria may in some embodiments be optimised to allow expression of the protein (e.g. in a wound) for 2, 3 or 4 hours or more.
Continuous expression and delivery of the protein is thus desirable and this may be afforded by using the transformed bacteria of the invention. By “continuous” or “prolonged” is meant that there is expression, and hence delivery, of the protein over a period of time e.g. over a period of at least an hour (or so, as discussed above). In particular this allows the protein to be effective over a period of time which is increased as compared to administration of the protein directly (i.e. as a protein product rather than by expression by the bacteria).
As discussed above, the nucleotide sequences encoding the protein(s) may be codon optimised for expression in LAB. Accordingly, in preferred embodiments the nucleotide sequences (or inserts) in the recombinant plasmids, which encode the proteins, may be selected from the codon-optimised nucleotide sequences shown in SEQ ID NOS. 1, 4, 7, 10, 13 and 16 which encode murine CXCL12, human CXCL12, murine CXCL17, human CXCL17, murine Ym1 and human Ym1 respectively, or a nucleotide sequence having at least 80% sequence identity therewith.
Thus in representative embodiments the recombinant plasmid may be chosen from the group consisting of the plasmids designated mLrCK1, comprising a nucleotide sequence as shown in SEQ ID NO: 1; mLrCK1.4, comprising a nucleotide sequence as shown in SEQ ID NO: 1; mLrCK1.7, comprising a nucleotide sequence as shown in SEQ ID NO: 1; hLrCK1, comprising a nucleotide sequence as shown in SEQ ID NO: 4; mLrCK2, comprising a nucleotide sequence as shown in SEQ ID NO: 7; hLrCK2, comprising a nucleotide sequence as shown in SEQ ID NO: 10; hLrMP1, comprising a nucleotide sequence as shown in SEQ ID NO: 13; and mLrMP2, comprising a nucleotide sequence as shown in SEQ ID NO: 16.
In some embodiments the plasmid of the invention comprises a nucleotide sequence which has at least 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89% 90%, 91% 92% 93%, 94%, 95%, 96%, 97%, 98% or 99% sequence identity to a nucleotide sequence of the following codon optimized inserts mLrCK1 (i.e., to the nucleotide sequence of SEQ ID NO: 1), mLrCK1.4 (i.e., to the nucleotide sequence of SEQ ID NO: 1), mLrCK1.7 (i.e., to the nucleotide sequence of SEQ ID NO: 1), hLrCK1 (i.e., to the nucleotide sequence of SEQ ID NO: 4), mLrCK2 (i.e., to the nucleotide sequence of SEQ ID NO: 7), hLrCK2 (i.e., to the nucleotide sequence of SEQ ID NO: 10), hLrMP1 (i.e., to the nucleotide sequence of SEQ ID NO: 13), and mLrMP2 (i.e., to the nucleotide sequence of SEQ ID NO: 16).
Sequence identity of nucleotide molecules may be determined by methods and software known and widely available in the art, for example by FASTA Search using GCG packages, with default values and a variable pamfactor, and gap creation penalty set at 12.0 and gap extension penalty set at 4.0 with a window of 6 nucleotides.
Such sequence identity related nucleotide sequences may be functionally equivalent to the nucleotide sequence which is set forth in SEQ ID NO: 1, 4, 10, 13 or 16. Such nucleotide sequences may be considered functionally equivalent if they encode polypeptides which would be considered functional equivalents to the respective CXCL12, CXCL17 or Ym1 proteins. Preferred functional equivalents are those which encode the preferred proteins as set out above.
In another aspect, the invention provides a bacterial strain transformed with the recombinant plasmid described above. The said bacterial strain is preferably a lactic acid bacteria strain such as a Lactobacillus strain or a Lactococcus (e.g. Lactococcus lactis) strain. More preferably, the bacterial strain is a Lactobacillus reuteri strain such as Lactobacillus reuteri R2LC or Lactobacillus reuteri DSM20016. The said strains (Lactobacillus reuteri R2LC/DSM20016 and Lactococcus lactis) are not found on human skin as determined by phylogenetic analysis of the forearm skin biota of six subjects (Ref. 13).
As well as the plasmids, expression systems, bacteria and kits, further products of the invention include pharmaceutical compositions and medical devices containing the bacteria. Such compositions and devices may include in particular wound dressings, packing materials, swabs, implants etc., or indeed any wholly or partially in-dwelling medical device which may be introduced or present at the site of a wound (e.g. at a surgical wound site), for example a line or catheter or implant. Also included are probiotic products, that is products containing the bacteria for administration to a subject, e.g. for oral administration, for example for consumption or ingestion, or for topical application to a wound or direct administration to a wound site, e.g. during surgery, or rectally, vaginally, etc.
Accordingly, the products (e.g. plasmids, bacterial strains, probiotics and wound dressings etc.) according to the invention are useful in medical therapy, in particular for promoting wound healing in human or animal subjects. As used herein, the term “promoting wound healing” means augmenting, improving, increasing, or inducing closure, healing, or repair of a wound. In preferred aspects of the invention, the human or animal subject is in need of wound healing due to an underlying medical condition leading to impaired wound healing, such as reduced peripheral blood perfusion (peripheral artery disease), hyperglycemia or neuropathy, or the subject may be immunocompromised for any reason, e.g. due to an underlying disease (whether acquired or inherited) or as an effect of medical treatment. In particular the subject may be suffering from diabetes.
The wound to be healed can include any injury, trauma or damage to any portion of the body of a subject. Examples of wounds that can be treated by the method include acute conditions or wounds; such as thermal burns (hot or cold), chemical burns, radiation burns, electrical burns, burns caused by excess exposure to ultraviolet radiation (e.g. sunburn); damage to bodily tissues, such as the perineum as a result of labor and childbirth; injuries sustained during medical procedures, such as episiotomies, trauma-induced injuries including cuts, incisions, excoriations; injuries sustained from accidents; post-surgical injuries, as well as chronic conditions; such as pressure sores, bedsores, ulcers, conditions related to diabetes and poor circulation, and all types of acne. In addition, the wound can include dermatitis, wounds following dental surgery; periodontal disease; wounds following trauma; and tumor associated wounds. Further examples are gastrointestinal wounds occurring during for instance gastritis or inflammatory bowel disease.
Thus the term “wound” is used broadly herein to include any breach of the integrity of a tissue or any damage or injury to a tissue. Thus the term includes any damage, trauma or injury to tissue or any lesion, howsoever caused (e.g. due to accidental injury or trauma, surgical or other intended or purposeful injury or disease). The trauma may include any physical or mechanical injury or any damage caused by an external agent including pathogens or biological or chemical agents. Tissue damage may also be caused by hypoxia, ischemia or reperfusion. Wounds may include any type of burn. The wound may be acute or chronic. A chronic wound may be described as any wound stalled in a healing stage, e.g. in the inflammatory phase, or any wound that has not healed in 30, 40, 50 or 60 days or more. The wound may be present in or on an internal or external surface or tissue of the body.
In a particular embodiment the wound is on an external surface or tissue of the body, e.g. it is a skin (i.e. cutaneous) wound or a mucosal wound, in particular a wound in an external mucosal tissue or surface of the body (e.g. in the eye, ear or nose etc.) In another embodiment it is a gastrointestinal wound. In a different embodiment it is not a gastrointestinal wound (i.e. it is a wound other than a gastrointestinal wound).
The bacteria may be administered in any convenient or desired way, e.g. orally, or topically, or by direct administration to a wound site e.g. by direct injection or infusion or application or introduction of a pharmaceutical composition or dressing or device containing the bacteria. In other embodiments it may be administered to the oral cavity, or intranasally or by inhalation, rectally or vaginally. The bacteria may thus be administered to, or via, any orifice of the body. For administration to a gastrointestinal wound the bacteria may be administered perorally.
The bacteria may be formulated or prepared in any convenient or desired way for administration by any of the above routes, according to procedures and using means well known and routine in the art. Thus, as well as pharmaceutical compositions, medical devices and dressings etc., the probiotic products of the invention may be formulated and provided as or in nutritional supplements or foods, e.g. functional foods.
Oral administration forms include powders, tablets, capsules and liquids etc. For topical administration, the product may be formulated as a liquid e.g. a suspension, or a spray or aerosol (powder or liquid), gel, cream, lotion, paste, ointment or salve etc. or as any form of dressing, e.g. bandage, plaster, pad, strip, swab, sponge, mat etc., with or without a solid support or substrate. Further the bacteria may be provided on (e.g. coated on) the surface of a medical device such as an implant (e.g. a prosthetic implant), tube, line or catheter etc.
The bacteria may be provided in any convenient or desired form, e.g. as an active or growing culture or in lyophilized or freeze-dried form.
The bacterial strains according to the invention can be formulated for topical or oral administration to treat surface wounds of skin or mucosa. Consequently, the invention further provides a probiotic product comprising a bacterial strain according to the invention. The said probiotic product is e.g. a pharmaceutical composition, preferably for oral administration. Alternatively, for topical application, the probiotic product is e.g. a lotion or a lotion-soaked wound dressing, comprising a bacterial strain according to the invention.
The product of the invention (i.e. the pharmaceutical composition or device or dressing etc.) may also contain the inducer (where an inducible promoter is used). This may be provided as part of the product (e.g. incorporated into or included in a dressing) or separately, e.g. as part of a kit or combination product, as defined above.
When co-formulated together in a product (e.g. a dressing or device) the bacteria and the inducer may be provided in a format in which the bacteria are separated from the inducer and are brought together (or contacted) in use. For example, the bacteria and inducer may be in separate compartments which are brought together (e.g. contacted or mixed), or may be separated by a barrier (e.g. a membrane or other partition) which may be broken or disrupted or opened in use.
Alternatively, the inducer may be formulated and provided separately (e.g. in a kit also containing the bacteria, or a product containing the bacteria), and the inducer and bacteria (or product containing the bacteria) may be brought together (e.g contacted) during use. This may be before, during or after administration to the subject. For example, a product comprising the bacteria may be administered first and then the inducer may be added or applied to the bacteria. In another embodiment the bacteria and inducer may be premixed before administration, e.g. just before or immediately before, or during administration.
Where bacteria are provided in lyophilized or freeze-dried form, it may be desirable to reconstitute, or resuspend, them prior to administration e.g. prior to or during use. This may depend on the wound and the format of the product which is used. For example, in the case of some wounds there may be sufficient liquid present to allow for the bacteria to be reconstituted/resuspended and become active. However, in other embodiments it may be desirable to provide a liquid for reconstitution (or alternatively expressed, for suspension or resuspension) of the bacteria. This may be provided in a separate vessel or container (e.g. as part of a kit or combination product) or in a separate compartment of a container, or vessel or device. The liquid may comprise or contain the inducer, or the inducer, when present, may be provided in a separate vessel or container or compartment. The liquid may be any suitable liquid for reconstitution or suspension of freeze-dried bacteria, e.g. water, or an aqueous solution, or buffer or growth or culture medium.
Thus, by way of example a two compartment system (e.g. in a dressing or device or container or vessel (e.g. a bottle)) may comprise freeze-dried bacteria in one compartment and a liquid in another. The liquid may optionally contain an inducer. In use, or prior to use, the two compartments may be mixed or brought into contact, and applied to the wound. In a more particular embodiment, the bacteria may be administered to a wound in liquid form, and a separate dressing may then be applied. It will be seen therefore that in one simple embodiment, a kit may simply contain a first vessel or container comprising the freeze-dried bacteria and a second vessel or container containing a liquid for reconstitution of the bacteria. Optionally the kit may also contain an inducer, which is also contained in the second vessel or in separate third vessel or container.
Hence, for example a said probiotic product preferably comprises an activation peptide capable of activating expression of the protein to be expressed in the lactic acid bacteria strain. The said activation peptide is preferably the peptide SppIP (i.e. a peptide comprising the amino acid sequence of SEQ ID NO: 19, or a sequence with at least 80% sequence identity thereto).
For cutaneous wounds, the said wound dressing can comprise freeze-dried bacteria in one compartment and an activation peptide in another compartment. When applied to the wound, the two compartments are brought together so that the bacteria are brought into contact with the activation peptide. Alternatively, bacteria can be contained in a gel-like structure on the adhesive side of a waterproof plaster or the side of the dressing in contact with the exudate. At the time of use, activation peptide is manually applied to the bacteria and the plaster or dressing is applied to the wound area.
Viable bacteria may also be comprised in a hydrocolloid, for example a natural gelatin. The bacteria can be incorporated by crosslinking into hydrocolloid e.g. gelatin films, plasticised and dried, retaining viability during storage until hydration. Viable bacteria may also be encapsulated within cross-linked electrospun hydrogel fibers. In this format the bacteria need not be freeze-dried.
For wounds in the gastrointestinal tract, a tablet is designed comprising at least two separate compartments, wherein one compartment comprises freeze-dried bacteria and the other compartment comprises liquid and an activation peptide. The tablet is squeezed before ingestion so that an inner membrane, separating the two compartments, is broken and the contents are mixed together. For wounds in the mouth (e.g. on the gums), bacteria according to the invention can be administered in a high viscous paste.
Specifically, formulations for topical administration to the skin can include ointments, creams, gels, and pastes to be administered in a pharmaceutically acceptable carrier. Topical formulations can be prepared using oleaginous or water-soluble ointment bases, as is well known to those in the art. For example, these formulations may include vegetable oils, animal fats, and more preferably semisolid hydrocarbons obtained from petroleum. Particular components used may include white ointment, yellow ointment, acetyl esters wax, oleic acid, olive oil, paraffin, petrolatum, white petrolatum, spermaceti, starch glycerite, white wax, yellow wax, lanolin, anhydrous lanolin, and glyceryl monostearate. Various water-soluble ointment bases may also be used including, for example, glycol ethers and derivatives, polyethylene glycols, polyoxyl 40 stearate, and polysorbates.
The bacterial strain can be provided in and/or on a substrate, solid support, and/or wound dressing for delivery of active substances to the wound. The solid support or substrate may be a medical device or a part thereof. As used herein, the term “substrate” or “solid support” and “wound dressing” refer broadly to any substrate when prepared for, and applied to, a wound for protection, absorbance, drainage, etc.
In an embodiment the invention provides a wound healing material or dressing attached to or comprising the transformed bacterial strain i.e. the dressing is a vehicle for administering the transformed bacteria of the invention. Alternatively the vehicle may be a plaster or bandage. The present invention may include any one of the numerous types of substrates and/or backings that are commercially available, the choice of wound healing material will depend on the nature of the wound to be treated. The most commonly used wound dressings are described briefly below.
Transparent film dressings are made of e.g. polyurethane, polyamide, or gelatin. These synthetic films are permeable to water vapor oxygen and other gases but impermeable to water and bacteria, have low absorbency and are suitable for wounds with low exudate), hydrocolloids (hydrophilic colloidal particles bound to polyurethane foam), hydrogels (cross-linked polymers containing about at least 60% water have higher absorbency and eliminate toxic components from the wound bed and maintain the moisture level and temperature in the wound area), foams (hydrophilic or hydrophobic e.g. polymeric foam dressings produced through the modification of polyurethane foam have good absorbency and are permeable to water vapour), calcium alginates (non-woven composites of fibers from calcium alginate from the phycocolloid group, alginates have a very high absorbent capacity. They also promote autolytic debridement because ion-exchange between the alginate and the exudate converts the insoluble calcium alginate into soluble sodium alginate, providing the wound bed with a moist, intact surface ideal for wound healing), and cellophane (cellulose with a plasticizer). The shape and size of a wound may be determined and the wound dressing customized for the exact site based on the measurements provided for the wound. As wound sites can vary in terms of mechanical strength, thickness, sensitivity, etc., the substrate can be molded to specifically address the mechanical and/or other needs of the site. For example, the thickness of the substrate may be minimized for locations that are highly innervated, e.g. the fingertips. Other wound sites, e.g. fingers, ankles, knees, elbows and the like, may be exposed to higher mechanical stress and require multiple layers of the substrate.
In yet a further aspect, the invention provides a method for wound healing in a human or animal subject, comprising administering to a human or animal subject in need thereof a bacterial strain according to the invention. The said bacterial strain is preferably comprised in a pharmaceutical composition or wound dressing as hereinbefore described. In such methods, the human or animal subject is preferably in need of wound healing due to an underlying medical condition leading to impaired wound healing, such as reduced peripheral blood perfusion (peripheral artery disease), hyperglycemia or neuropathy.
Results obtained and included in the Examples below demonstrate the advantages of the invention. In particular, improved wound healing (e.g. in terms of better or faster wound closure) may be obtained by using the protein-expressing transformed bacteria of the invention, as compared to, for example, a protein preparation directly (i.e. just the protein, no bacteria) or just bacteria alone (bacteria which are not modified to express the protein, e.g. not containing the recombinant plasmid). Further, an improved effect may be seen when bacteria are administered to wound, compared to administration of a supernatant obtained from a transformed bacterial culture. It is thus advantageous to deliver the protein to the wound by means of a lactic acid bacterial host expressing the protein. It is believed that there may be synergistic effect. In other words there may be a synergy between the effect of the bacteria and the effect of the protein on wound healing. Accordingly, in some embodiments there may be a greater than cumulative effect of the transformed bacteria on wound healing, relative to the effect of corresponding untransformed bacteria (i.e. not containing the plasmid) and the effect of the protein when provided as a protein (i.e. not expressed from bacteria in situ).
It is believed in this respect that the effect of the bacteria in lowering pH e.g. in the site of the wound may assist in augmenting or enhancing or promoting the activity of the protein. Whilst not wishing to be bound by theory, it is further believed that administration of the transformed bacteria according to the invention may have a beneficial effect in promoting macrophage activity at the site of the wound. For example, the number of macrophages may be increased.
The effect of the transformed bacteria on wound healing may or may not be immediate, and may take some time to be seen (e.g. 1, 2, 3, 4, 5 or 6 or more hours to be seen, or longer, e.g. 8, 10, 12, 15, 18, 20 or 24 hours or more, or 1, 2, 3, 4, 5 or 6 or more days to be seen, or longer e.g. 8, 10, 12, 15, 18, 20 or 24 days or more, before improved wound healing can be observed). For chronic wounds in elderly humans it may take longer to see a difference between the treatment group and control group for example it may take around 12 weeks.
A particular and important utility of the present invention lies in the treatment of chronic wounds, particularly ulcers and in particular in the treatment of diabetic foot ulcers.
The prevalence of chronic foot ulcers in persons with diabetes is about 18%. In 2013, the European population reached 742.5 million, which translates into 32.7 million with diabetes, of which 2.9-5.8 million have chronic foot ulcers. Mean duration of an ulcer of this type is in the range of months where less than 25% of the wounds are healed within 12 weeks when standard care is given. The end stage of this condition is amputation of the affected limb. Today the treatment of people having chronic foot ulcers is divided between primary care, home care, nursing homes, relatives, self-management and visits to hospital wound clinics. The current treatment relies on off-loading, removal of dead tissue using surgical debridement, repeated changes of wound dressings, systemic antibiotics and in special cases treatment with living larvae or collagenase and at a few locations in Sweden hyperbaric oxygen treatment can be offered. If an underlying cause also includes obstructions of larger arteries, this can be corrected surgically by bypassing vein graft. Today the wounds are treated every second to third day. Treatment with the suggested modified lactic acid bacteria in any of the suggested forms or formulations would not disrupt this practical routine. Improved healing of such wounds by the treatments of the present invention would thus be of considerable economic benefit, as well as of personal benefit to the patient.
The bacteria are active and produce and deliver the encoded proteins to the wound surface for a period of time (e.g. about one hour) in vivo. They may then become inactive and die. Slow or dead lactic acid bacteria can with no risk be in the wound/dressing environment until the dressing is changed as normal.
The biotherapeutic according to the present invention will have significantly lower production cost compared to protein drug compounds. This is because the biotherapeutics produces the active protein itself directly in the wound.
Open wounds such as diabetic foot ulcers, together with loss of function in the foot, cause considerable discomfort, and even disability to the patient, and can have a significant negative impact on quality of life, including significant risk or infection and therefore prolonged use of antibiotics, and ultimately amputation. Improved healing would thus be of tremendous personal benefit to the patient and would also have the benefit of reducing antibiotic use (and consequently the spread of antibiotic resistance). It is believed that treating such chronic wounds according to the invention may amplify endogenous alarm signals in the wound, and kick start the healing process in stalled or chronic wounds, and accelerate healing time.
Further, the invention may have advantages in flexibility and ease of use by medical staff.